And moses e



G. R. BLODGETT, R. T HURLEY, AND M. E. CHENEY.

SPARK PLUG.

APPLICATION FILED JAN. 5. 1922.

m 3 O n 3 u QN m w 3 k w s N me a Reissued Mar. 14, 1922.

IN VEN TOR 15,303 3 SHEETS SHEET 2.

SPARK PLUG.

APPLICATION FILED 1AN.'S.1922.

G, R'. BLODGETT, \R. T. HURLEY, AND M. E. CHENEY.

Beissued Mar. 14, 1922.

aka

IN VEN TOR G. R. BLODGETT, T. HURLEY, AND M. E. CHENEY.

SPARK PLUG.

APPLICATION FILED rAN.5.1922.

Z 5 J 7 m 5H W 7 7 W 4 Reissued Mar. 14, 1922.

INVENTOR George, 7843/00 96)? #0565 E G/zeney Roy THMr/) UNITED. STATES- PATENT OFFICE.

GEORGE a nnonen'rr, or BROOKLYN, ROY 'r. HURLEY, or NEW YORK, AND moans E.-

CHENEY, or BROOKLYN, NEW YORK.

sranx rune.

Specification of Reiss ued Letters Patent: Reissued Mar, 14, 1922,

Original Zfio.'1,399,376, dated December 6, 1921, Serial No. 509,482, filed October 22, 1921. Application for i reissue filed. January 5, 1922. Serial No. 527,170.

To all whm it may concern:

' Be it known that we, GEORGE Roy T. HURLEY, and Moses E. CHENEY, cit-izens of the United States, the said BLOODGETT and CHENEY residents of Brooklyn, county of Kifigs, and State of New York, and the said URLEY, a'resident of Bronx, county of Bronx, and State of New York, have invented new and useful Improvements in Spark Plugs, of which the following is a specification.

Our invention relates toimprovements in spark plugs. It has for its object to bring about the production of spark plugs better adapted for the particular uses to which they are to be put and to produce spark plugs. more eflicient and durable and lesslia'ble to carbonization and pro-ignition in use than has heretofore been possible. It consists'of the novel devices herein set forth.

Heretofore many attempts have been made to overcome the troubleso'f carbonization and pre-ignition so frequent in the use of spark plugs. But so far none of these attempts have been-entirely satisfactory or successful in overcoming the troubles. While many expedients have been suggested, more or less successful under certain specified conditions,

none of them have'resulted in the production of spark plugs uniformly and durably free from these troubles.

We have discovered that there is a close re- 7 lationship existing between the. volume of the space within the spark plug surrounding the electrode and adjacent parts, into which space the gasflows from the cylinder and in which it is burnt, the area of the walls of such space effective to receive, maintain and dispense heat, the manner and extent of admission of gas into the space, and the compression ratio of the engine cylinder with which the spark plug is to be used, and that, if the pro er arrangement and proportions are secure in the manufacture of the spark plu s in these factors'or particulars, the resultmg spark plugs produced Wlll be well adapted for the particular use s to which .range of compression ratios and under much greater changes in load conditions, will be freer from liability to carbonize or to prei ite and will enerally give much more e cient and satis actory results; the gas introduced into the spacewithin the spark plug will be brought into the very best condition for combustion, and the parts of the spark plug with which the gas comes into contact will'be under ordinary running conditions brought into and maintained within the proper limits of temperature to produce the best results, neither low enough to permit ca-rbonization or high enough to cause pro-ignition. The gas itself will be brought into the most favorable condition, both as to compression and complete vaporization of the fuel, for complete combustion; thus securing the highest efiiciency without leaving harmful products of combustion on the electrode,

insulation or other parts.

'part hereof, we have illustrated our improvement in its preferred forms for varyin conditions. Referring to the drawings, igure 1 represents a spark plug adapted for use with engine cylinders having a high com: pression ratio, such as are used for aviation purposes. Figs. 2 and 3 represent spark plugs adapted to be used with engine cylinders havinglow compression ratio, F g. 2 Y

I three figures, the

I tral section through in a space formed within the surface of l of the shell,

7 temperature, properly at the proper moment, 1. maintain it within the proper limits oftemillustratin for marine purposes. In each oftheseview is a central vertical section through the greater part of the spark plugs. Fig. 4:1BPIGS8IitS a cei1 an engine cylinder hav- 1ng a high compression ratio. Fig. is a similar View for an engine cylinder having a low compression ratio, each figure showing a spark plug especially adapted for use with the engine cylinder with which it is connected. Figs. 6 and 7 represent spark plugs of a specific core and shell construction used for test purposes as hereinafter described.

, 'Referring to Fig. 1, 1 represents the shell ofthe spark plug,

2 a central electrode, 3 the insulation surrounding it, 4 the other electrode, and 5 a gasket between the'insulation and the shell. All the parts of the spark plug are not shown in detail. 6 is a part of the insulation protruding downward toward the end of the central "electrode 2. 7 lower part of shell 1, the walls of the space consisting of the interior surfaces of shell 1 and the exterior surfaces of the lower part of electrode 2 and of protruding portion 6 of the insulation. This space is of course filled with gas at each operation of the engine cyl inder, which gas is exploded at the proper time during such operation. We have dis covered that this space and the area of the its surrounding walls effective to receive, maintain and dispense heat, and the cross-sectional area of the orifice 8, should be proportioned and arranged with reference to the compression ratio adapted to be developed under ordinary running conditions in the enginecylinder with which the spark plug isadapted to be used, and when the proper relationship of the volume of such space, and the effective heat area of C, the surrounding Walls and the cross-sectional area of-the orifice to one another and to the v said compression ratio is obtained, the electrode and its adjacent parts, and the walls proper range of to condition the gas for the most complete combustion-possible e., to bring it to and conditions be kept within a perature, on theone hand above the carbonization point, i e not low enough to permit carbonization, and on the otherhand below the pre-ignition point, if" e., not high enough to cause pre-ignition. In general, the volume of such space: and the effective heat area of its surrounding walls should be decreased as the compression ratio increases and) increased as that ratio decreases, although the rate of such decrease or increase is not exactly proportioned to the rate of increase or decrease in the compression ratio.

one adapted to be used with engine cyl nders for automobiles, and Fig.

, fective heat areaj? etc.

will under ordinary running" Generally speaking, the orifice should be more or'less restricted, dependingupon the compression ratio. In general, 'as the compression ratio becomes ,higher, the orifice shouldbecome larger in cross-sectional area,

although this does not exactly vary in direct proportion tothe rise in compression ratio. In other words, speaking compression ratio is high the area of the orifice should be larger and if the compression is lower the cross-sectional area of the orifice should be less. a

The area of the walls of the space, referred to herein as effective area or eftual physical surface asmerely measured in square centimeters but to the total of the heating capacity of those walls. These walls in spark plugs are composed of a' number of different substances, of the shell of metal, the exterior wallsv of thespindle and electrode usually of a different metal, the exterior walls of insulating material, which may vary in different plugs,

Manifestly the total of efiective heating workfor capacity therefor in .the walls is the sum of the' products of the areas of actual physical surfaces by-the said relative face, such capacity being the ratio of the actual temperature of the said surfaceun- 'der normal running conditions to the temperature required to condition fuel i. e. the temperature just below that of the tion point. This for conciseness the effective area or effective heat area and each of the terms is used with this meaning throughout the specification and claims. the parts under normal running conditions can be ascertainedin any of the ways known to those skilled in the art, such as by the use of sentinel salts-or pyrometers. To give an illustration of effective area of anypart such as the surface ofthe central electrode, we will assume that the actual physical surface of the electrode in any particular case is one square centimeter. The actual normal running conditions of the surface ofthe electrode is determined to be 1900 F. absolute and the temperature required to condition the fuel in this particular case is we term 1135 F. absolute, then the effective heating 139 generally, if the refers not to the total ac- .80

such as the inside walls These substances have different heat There are thus two facabsorb, hold and give out heat heating capacity of each surpre-igni 11C) The actual temperature of any of the method of computing the temperature under still.

1900 1135 which. is l.67+ square centimeters.v The effective area of each of the other parts is computed in the same way. 1

Figs. 2 and 3 illustrate spark plugs'adapt ed to be used with engine cylinders of a relatively low degree of [compression ratio. The spark plug of Fig. 2 is adapted to be used with en ine cylinders of automobiles, and that of ig. 3 with engine cylinders of uct of its area 1 by the ratio of marine engines, in which the compression ratio is still lower than that of engine cylinders adapted for automobile use. The corresponding parts of the spark plugs of Figs. 2 and 3 are-numbered tov correspondwith similar parts of the spark plug of Fig. 1.

-In Fig. 2 it will be noted that the space 7 is larger or has a larger volume than that in Fig. 1, and the space 7 of Fig. 3 a still larger volume, and the surface area of the parts constituting the walls of the space in Fig. 2 is lar er than that of the corresponding parts in i 1, and in'Fig. 3 it is larger The ori ce 8 of the spark plug of Fig. 2 has a cross-sectional area of less size than that of Fig. 1 and the orifice 8 of Fig.

3 a still less size, although these areas in Figs.-2 and 3 are closer to each other than either one-is to that of Fig.1. In Figs. 2 and 3, the restricted opening 8 in each case is shown .as-made by means of a cap 10 having a restricted circularfcentral open.-

in v Fig. 4 is a central section through an en-' gine cylinderhaving a relatively high compression ratio and represents an engine cylinder such as the spark plug of Fig. 1 is adapted to be used with. At -its upper end it is shown connected to a spark plug similar to Fig. l. Fig. leis drawn diagrammatically to represent the range of displacement and corresponding compression ratios in high ratio compression cylinders. For this purpose" the left half of the figure represents substan-" tially about the highest limit of displacement or ratio of compression, and the right hand part of the figure represents about the lowest limit of displacement and the lowest limit of compression ratio iIihigh compression cylinders, as defined herein. In each half 11 represents'the lower en'd'in each case of the cylinder and the distance between that in each instance and the dotted line 12 represents the length of stroke of thepiston, and the distance from the dotted *lines to the upper end of the cylinder represents in each instance the compression chamber ofthe cyl inder. In each case the stroke is seven inches. In the'left hand half the compression chamber is 1.4 inches in length and in the right'hand half it is 1.75 inches in length. 13 represents the outer walls of the cylinder, 14 the inner walls, and 15 an intervening space for a cooling fluid. The other partsof the cylinder and its connections are not .shown in detail, being of any ordinary construction and forming no part of our invention.

Fig. 5 similarly represents a verticalsection through an engine cylinder of low compression ratio, as defined herein, and adapted to be used with a spark plug for automobiles or marine engines such as shown in Figs. 2 or 3. In this view similar parts are correspondingly marked to those of Fig. 4;

The left hand side of the cylinder ,of F ig.- 5 represents a length of stroke of piston of 4 inches and a compression chamber of 1.6

inches in length, forming substantially about the lower limit of compression ratio used in this class, one with which the spark plug of Fig. 3' is adapted to be used. The right hand end illustrates an engine cylinder in which the piston has a stroke of 5 inches and the compression chambera length of 1.25 inches, and represents substantially about the upper limit of compression ratiointhis J I class. It shows more particularly anengin'e cylinder with which the spark plug of ig 2 is adapted to be used.

While the limits of compression ratio and corresponding limits of volume of the space surrounding. the electrode. and adjacent parts and of the effective area of the surface, of the walls of said space cannot be stated exactly r0 the different classes of compression cylinders, we have found that under ordinary running conditions they are about as follows: For high compression engines, namely, those in which the compression ratio under ordinary running conditions wilLrangehigher than about 5 to 1 and will generally range from about 5 to 1 to 61} to 1, the'volume of thespace should range from about 1.25 cubic centimeters to about .50 cubic centimeters, and the effective area -of the surface of the walls of the space should rang'e'from about 15 square cent1meters to about 3 square centimeters; in low compression engines or those in which the limits ofthe compression ratio under ordinary ru-nning conditions will range below about 5 to 1 and generally from about 3 to 1 to 5m 1, the .volume of the space of the spark plug should, vary from about 1.7 5 cubic centimeters to about 1.25 cubic centimeters and the surface of the walls of said space from an area of about 36 square centimeters to about 13 square-centimeters.

Restriction of the orifice and especially in proper relationship to the other factors re: f rred to above, assists in securing the proper amount of gas in"th e spark plug on each operation and in bringing that gas to the proper temperature and condition for explosion. Where an opening'to a spark plug is unrestricted there are apt to be devious currents interferring with bringing the gas into proper condition for explosion, while with a restricted opening there is a positive swirling flow inward before explosion andoutward after, explosion, and the fuel fluid is more thoroughly brought into contact with the walls of the space inside of the plug, tending to bring it into proper condition. u i

The restriction ofthe orifice tends also to separate the space inside of the spark plug from the space inside of'the cylinder more than would otherwise be the case, thus preventing too great and'sudden rushes. from the cylinder of cold gas before explosion and of intensely heated gas after explosion, and

- also permitting the gas within the space in the spark plug to be broughtinto better condition for combustion than is possible with the gas in the cylinder generally.

In high compression engines where the compression ratio variesas above stated, the

' cross-sectional area .of the. orifice should vary from about 0.20 square centimeters to about.;1 .-0 square centimeters. In low compression engines within the limits of com pression ratio above stated, we have found that the cross-sectional. area of the orifice should vary from about 0.10 square centimeters to about 0.20 square centimeters.

One application of our improvement is to take any specific core and shell construction of spark plug, meaning by that a special arrangement, form, shape, size, etc, of central spindle, surrounding nsulation, central electrode and surrounding shell, etc and vary or adapt the orifice to cause such spark plu to become fitted for use .with any desire compression ratio of enginecylinder, or to adapt it so that it will cover a wide range of compression ratios. While this can be carried out underthegeneral principles laid down above, we have discovered that the best cross-sectional area of orifice in such instances cited can be derived from the following formula, naniely .OzKr, in which 0 represents the cross-sectional area of the fiorifice, r the compression ratio of the cylinder, and in which K and n are constants of the particular core and shell construction.

. results.

The value of the constants K and n for any particular core and shell construction can be determined by taking two spark plugs ofthe same core and shell construction exceptv that the orifices in the two cases will vary. r The two plugs are then tested upon cylinders of different compression ratios until in each case the compression ratio is determined with which the spark plug gives best Such tests are well known to those skilled in the art and need not be described in detail exceptto say that in making such tests the highest compression ratio in each case is determined with which the spark plug will function without preignition-and that compression ratio is taken as that at which, under normal running conditions, i

meaning. For example, in Figs. 6 and 7, we

have illustrated a spark plug having the same core and shell construction but with varying orifices, that of Fig. 6 having a cross-sectional area of orifice of .82 square centimeters and that of Fig. 7 a cross-sectional areaof orifice of .215 square centimetors. The two plugs also differ slightly in some other dimensions, which do not, how ever, prevent them from being of the same general core andshell construction. In Fig, 6, the inside diameter of the shell is sevensixteenths of an inch and in Fig. 7 onequarter of an inch, and the side electrodeof I Fig. 6 is .086 in diameter and has a length of .1212 inches, while that of Fig. 7 has the same diameter but a length of .0375. The central electrode has a diameter of .125 inches in each plug. tests that the spark plug of Fig. 6 was bestadapted for use with a-compression ratio of 6.5 to .1, while the spark plug of Fig. 7 was best adapted for use with a compression ratio of 5 to 1.

\Vith the above specific examples of the core and shell construction in question, the values of K and n are derived from the above formula, as follows: the formula representing the plug of Fig. 6 is OzKr, and that representing the plug of Fig. '7 is 0,:Krf. From these two equations the values of K and n are derived as follows: In the first,

and in the second case Therefore,

Multiplying by we getv It "was found in the 1 Substituting values of O, 0 1' and 1' The values of all the factors now being known, the value of O- can be determined in the original formula, O=Kr.

As a specific example, if -'t wasv desired to determine the O-most suitable foruse with the compression ratio 6t0'1, with the same.

core and shell construction, it would be done,

as follows: v r

This cross-sectional areais net cross-sectional area and of course allowance should be made because of the central and side electrodes. When' the cross-section of the central electrode and the projected surface of theside electrode are added to the net, the

gross area becomes .655 I square centimeters, requiring a diameter of orifice of .913 centi-v meters, or approximately .359 inches.

Our improved spark plugs are durable,

'- efiicient, not liable to carbonization or preignition-in use even over a wide range of com ression ratios and load conditions.

at we claim as new and desire to obtain by Letters Patent is:

1. Ina spark lug adapted for use in connection with cylinders of internal combustion engines having a compression ratio higher than 5 to 1, the combination of an .electrode and a shell rovided with a space,

to be filled with gas rom the cylinder, surrounding the electrode and' adjacent parts, and a restricted orifice adapted to connect the space with the cylinder of an engine, the

relative proportions of the volume ofthe space within the spark plug and the effective area of surface ofthe walls of said space and the cross-sectional area of the orifice to one meters, the effective area of surface of the walls of said space being within about 13.

square centimeters to about 3. square centimeters, and the cross-sectional area of the orifice being within about 0.20 square centimeters to about 1.0 square centimeters.

2. The combination of a cylinder of an internal combustion engine having a high compression ratio, a spark plug fitted into a wall of the cylinder, having an electrode and ashell provided with a'sp'ace, to be filled with gas from the cylinder, surrounding the electrode and adjacent parts, and a restricted orifice adapted to connect the space with the cylinder, the relative proportions of the vol-' ume of the space within the spark plu orifice to one another being substantially as and i the effective area of surface of the we ls of 7a said space and the cross-sectional area of the follows: the volume of said space being within about 1.25 cubic centimeters to about .50 cubic centimeters, the effective area'of the in about 13. square centimeters to about 3.

' surface of the walls of said space being withsquare centimeters, and the cross-sectional,

area of the orifice being withinjabout 0.20 square centimeters to about 1.0 square centimeters. e

'3. In a spark plug adapted for use with a specific compression rat-i0 or range of comressionratios of cylinder of internal comustion engines, the combination of a specific core and shell construction containing a. space around the electrode and adjacent parts of a specific volume and having a specific effective area of surface for the walls of said space, and a restricted orifice for said space of a cross-sectional area of the value of O in the formula O:Kr, where K andn,

are constants dependent upon the said construction of. core and shell, and are determinable from two spark plu s of the said construction of core and she] but difl'ering from each other in cross-sectional area of orifice, when each spark plug is used with the compression ratio adapted to give the best results for said spark plug.

4. The combination of a cylinder of an internal combustion engine of a specific compression ratio, a spark plug fitted into the walls of said cylinder, and having'a specific construction of core and shell containing a space around the electrode and adjacent parts of a specific volume, andhaving a specific effective area of surface for the walls of said space, and a restricted orifice to the spark plug of a cross-sectional area of the value of O in the formula OzKr, where K and n are constants, dependent upon the said construction of core and shell and are determinable from two spark plugs of'the said construction of core and shell but differing from each other in cross-sectional area of orifice, when each spark plug is used with the compresslon ratlo of cylinder adapted to give the best results from said spark plug.

5. The combination of a cylinder of an internal combustion engine having a high compression ratio, a spark plug fitted into, a

wall of the cylinder, having an electrode and a shell' provided with a space, to be filled with gas from the cylinder, surrounding the electrode and adjacent parts, and a restrioted orifice adapted to connect the space with the cylinder, the relative proportions of the volume of the space Within the, spark plug and the effective area of surface of the Walls of said space and the cross-sectional area of the orifice to one another being substantially as follows; the volume of said space being Within about 1.25 cubic centimeters to about Q50 cubic centimeters, the effective area of the surface of the Walls of saidspace being mace within about 15. square centimeters about 3. square centimeters, and the cross-sectional area of the'orifice being Within about 0.20

square centimeters to aboutlf) square centi- 15 meters. a

In testimony whereof we have signed." our names to this speelfication.

GEORGE R; BLODGETT. ROY T. HURLEY. MOSES E. CHENEY. 

